Keep your swimming pool clean, clear and algae-free with Blue Waves premium Black Zapper Algaecide! Algae growth is common when your pool has poor circulation and when the disinfectant level or algaecide content in the water is low or neglected. The powerful black algaecide has been formulated specifically to kill and prevent tough black algae strains! Not only does Blue Wave algaecide kill existing strains, but it also prevents the formation of tougher, resistant algae. The super concentrated formula of Black Zapper is non-clouding and low-foaming.